Force-ratio measuring and computing device



June 19, 1951 R. F. GARBARINI 2,557,092

FORCE-RATIO MEASURING AND commas nsvxcs Filed April 24, 1946 INVE NTOR [/6 5'0 SEA 7" E GhRBAR/N/ JZWWAQ, W ORNEY Patented June 19, 1951 FORCE-RATIO MEASURING AND COMPUTING DEVICE Robert F. Garbarini, Woodside, N. Y., assignor to The Sperry Corporation, a corporation of Dela- Application April 24, me, Serial No. scum 1 22 Claim.

This invention relates to force-ratio measuring and computing devices. More particularly, the invention comprehends the fabrication and use of novel, self -contained instruments for simultaneously measuring and comparing a pinrality of interdependent, variable and varying force-ratios, and delivering torque outputs for operating equipment and mechanical power systems as functions of such force-ratios.

This invention also relates to improvements in special force-ratio measuring instruments, and, more particularly, to computers wherein functions of ratios between forces being measured, any or all of which are continuously variable, are automatically varied or compensated according to variable factors, such as temperature effects, to give true measurements, which can be transmitted to controlled devices or systems with sufficient power to drive same.

The instruments utilized herein are characterized by a number of other features of importance and novelty, including a substantially rigid, yet mobile, shock-proof, low hysteresis, variable fulcrumed lever force-ratio measuring device, which is maintained in balance by special pivotpositioning means, accompanied by appropriate vibration (dithering) of the lever, and forceapplying elements, to give a fluid, quick response to any and all control or modifying factors applied thereto.

The invention provides a novel force measuring apparatus in which, during normal operation,

under static equilibrium conditions of the system, a fulcrum is mounted for reciprocation along, and in parallel relation to, the longitudinal axis of a lever, and is driven, unilaterally, by a constant speed motor, to a position of unbalance of the lever. A servomotor is effective, upon unbalance of the lever, to restore the fulcrum to the equilibrium position. This gives the fulcrum an inherent, cyclic, oscillating translation about its equilibrium position, the magnitude of which is a function of the inertia, and motor torque characteristics of the balancing system, described herein. When a change occurs in the ratios obtaining between the control forces, the lever is unbalanced and rotates, in the direction of the dominating force-moment, to open or close the circuit of the unidirectional motor to effect translation of the fulcrum to a new, lever-balancing position. The application of a dynamic force to one end of the lever will rock the lever in the direction of the applied force, and thereby increase the time of engagement of contacts controlling the servomotor circuit or vice versa, de-

2 pending upon the specific instrument which will serve to cause the translation of the fulcrum to the new equilibrium position demanded by the change in the applied force.

The fulcrum will be mounted for reciprocation on a bed or in tracks which are parallel to the normal, horizontal, static-equilibrium position of the lever. The fulcrum may desirably comprise a shaft having a positive bearing against the lever, which is maintained thereagainst by the special mounting features of the assembly. The ends of the fulcrum shaft will be mounted in frictionless roller bearings contained in cages rotating on the fulcrum tracks. These fulcrum tracks may be grooved or channeled to prevent any transverse motion of the fulcrum cage with respect to the longitudinal axis of the lever supported thereon. Such an arrangement will insure the desired static rigidity of the system, while permitting its utmost flexible operation under conditions of use in any position or orientation in space. Even while operating under such flexible conditions, the instrument assembly will maintain its structural rigidity, insuring substantially shock-proof mounting of all the elements in the instrument casing, and preventing damage thereto under conditions of applied shock. Such an instrument mounting or assembly will be especially suited for use in aircraft, and in artillery and other gun installations, which are normally subjected to heavy vibrations and shocks of undeterminable and unpredictable quantity, amount and occurrence.

Further objects and advantages of the present invention include force-ratio measuring instruments generally, of predetermined structure, whose elements can be calibrated for use in a variety of force-responsive systems and which can be incorporated, as functional units or entities, in control systems for automatic operation of same in response to changes in mutually interdependent factors over a wide range of simultaneous variations of said factors.

The factors of novelty herein will be described with particular reference to the drawings in which there is illustrated, by way of example, a novel force-ratio measuring instrument for providing an indication of true altitude.

In the drawings, like numerals refer to similar parts throughout the several views, of which Fig. l is an isometric drawing showing the mounting of the movable parts of a force-ratio measuring instrument, and the controls therefor;

Pig. 2 is a schematic diagram of the system of Fig. l as mounted in a casing;

'changeaandhas functionof eratiooftwo forces; and

Fig.5isaviewsimilartol'ig.4showinga special fulcrum control.

Altimeters hitherto used indicate pressure altitude only. altitude values are not usable for computing until they have been converted to tude values. In order to arrive at true Thisfactoris amtemiseumand time-consuming. aodtiallyforuseinmhter p1anes,andothercraf twhicharemannedbya single pilot as a one-macaw.

The true-altitude meter described herein, by way of example, incorporates the novel forceratlotsoastogiveamcter oreomputerwhichhasmalllagduringaltitudc tpower to drive other Theequation for altitudeusedhereinisasfolion:

(1) H=KT.. 10;

or (2) H=KTar (10 Pr-log P8) mmairattargetorgroundlevel.

Equation in shows that the true altitude is a w P-i-andPs. ortwoi'iftheareaover hichthepressuresactis asimity. Ameasureofthis ratiocanbe astheinstantpositionof thefulcrmnfiofaleverwhenthetwoforce-mo- (Thhisillustratedinl'igs.

mthbe'tweenthepoints w observed pressure altitude values betweenfulerum i2 andtheends ll and "will bedesignatedasaandb.respectively. w

The equation of the moments of force bout fulcrum if is, therefore, ,r

(3) aPs=bPr From the diagram it will be seen. that (4) d=L-b where L is a constant. Substituting the value for a from Equation 4 in Equation 3. there is obtained a value for b according to the following equation:

' equation.

ltquationfishowsthatthearmbisameasure oftheratio 4 The position of fulcrum I! can be calibrated, therefore. in this ratio.

Where one of the forces is eomtant, as, for example, target pressure (PT); the force ratios will be determined by the variation in the complementary force, e. g. static pressure (Pa).

The pressure forces can be balanced automaticallybytrsnslating fulcrum if bymeansofa servo unit, as shown in Pig. 4. In this showing. the fulcrum I2 is shown mounted for lateral translationononeendofanarmllhavingrack I! at its other end. Oontast- 2|, mounted at oneendoftheleverarm,engageswithacooperatin: stationary contact 23 when the lever unbalanccs in a coimter-clockwise direction closing the circuit of an intermittently operable n servomotor II havingashaft 2B which drives one input of a subtracting differential. llsecond inputofthedifferential is operated by a constant speed motor 21. apinionllinmeshwithrackllismountedonoutputshaft 3| of differential 28 and is effective to displace fulcrum ii in accordance with the diflerence between the displacements of the inputs of the differential. Motor 21 constantly tends to translate fulcrum I! in such di-' rectionastoclosecontactsll and. Inl'lg.4 motor 21 constantly translates the fulcrum unidirectlonallytobalaneetheleverinacounterclockwise direction. Since motor 21 is operated contimiouslyitwillcausethelevertobedisplaced fromunbalanceinonedirectiomthroughequilibrium, to an unbalanced condition in the opposite direction. In the latter condition, contacts ii and 23 will engage and close the operating circuit for motor ll. Motor 2| actuates the differential at twice the speed of motor 21, and thereby reverses the direction of the displacement of the output shaft 3. of the differential and fulcrum ll torestorethelevertoapositionof equilibrium whereupon contacts 2i and it open causing motorlltostop. Asmotor IIisconstantly operat ing,thecycleiustdescribedisconstantlyrepeated,andtheleverismaintainedinastateof dynamic equilibrium about itsfulcrum. The dis- Ltheforcearmsformed 7 placements! fulcrum i2 inthcarrangements the forces Po and Pr showninFigs.3and4isaccordingtoanonlinear function of (Equation 5) In Fig- 5, fulcrum I: of lever II is actuated by a barrel cam 35, which is displaced by the output shaft of difl'erential 26. The differential is actuated by motors 24 and 21 in the same mannor as the corresponding diflerential 26 of Fig. 4. The cam is formed with a spiral cam groove 86 in which rides a cam follower I! attached to In the diagrams considered immediately above,

have been shown as parallel arrows applied at the points l4 and ii of lever Ill. Actually, the forces could be applied by stretching a spring attached to the lever, or by a bellows arrangement fastened to the lever, or by any other suitable force applying device. An arrangement of the kind Just referred to is shown in Fig. 2 where a lever ll enclosed in a casing 40 is provided with a movable fulcrum II. A spring 4| having one end fastened to the lever at point It thereon and the opposite end attached to a rack 42 is used to apply a force to the lever. A pinion 43 on shaft 44 in mesh 4| in accordance with the static pressure P'r at the target.

An evacuated bellows installation, which pres- I'he bellows will anv l sure is designated as Ps.

a force to the lever in accordance with variations in altitude pressure Po.

Fulcrum I2 is shown in Fig. 2 as mounted on a sliding support 2| which projects outward 6 once the opposite springs forces Pa and Pr are set force Pa may be conveniently made ing bellows 48 to the atmosphere.

In the device as shown in Fig. 2, true altitude will be indicated as a resultant of the forces applied. On turning the Pr knob 45. the tension of calibrated spring 4! is adjusted. As the characteristics of the spring are linear, the change of force will be directly proportional to the rotation of the knob. This is a distinct advantage, in that it makes for simplification of construction and of manipulation. Static air pressure in the casing, acting on the evacuated bellows 4|, will give a force, Ps (altitude pressure), applied at the point l4 of the lever. If the area of the bellows is unitary, the force acting thereon will be equal to the static air pressure Pa. The compensating spring 55, as noted, balances the bellows, which is initially set up in tension, so that,

and bellows when the at zero. The bellows zero by openon the unbalance of is not at the exect mined Lever II should have but one degree of freedom, and this should be in rotation about its fulcrum II, This condition is obtained by a novel mounting for the lever shown in Fig. 1. In this figure various parts are shown supported by a bracket 0..

In Fig. l. lover I. is shown as being surmorted by a flat spring ll attached to one end of the lever and dlspoud in alignment therewith, one end of the spring being secured to an upright 82 of bracket ii. The opposite end of the lever is supported by flat spring I. Spring 63 is fas 15 disposed and 11 formed in a movable fulcrum Ball bearing members 85 and 86 disposed on the fulcrum shaft near opposite ends thereof support respectively a pair of members depending from a guided by an opening in upright 62. Rod 88 engages the surface of a vllthalongpinionlllflxedona 7 three-dimension cam llI follower therefor, the cam the position of the carriage and thereby the fulcrum shaft ll underneath lever II. Spring OI attached to carriage I! and to upright 82 serves to hold cam follower 88 against the cam.

An adjustable spring lI similar to that shown in Fig. 2 is attached to the lever III. The upper end of the spring is fastened to the lever and the lower end to a screw 90 which extends through openings in spaced horizontal members I and III' formed on a member III rail II. A nut Ill having a worm gear formed thereon is threaded onto screw 09 and is disposed between members I08 and III. The nut III is turned for the purpose of adjusting spring ll by a knob n; The knob, turns a worm, not shown, in mesh with the worm gear on nut I.

As in Fig. 2 a dial 46 is fixed with respect to knob do and cooperates with a stationary index 41. A spring 50, corresponding to that of Fig. 2 is attached to the lever It by a link I05. The upper end of the spring is supported by an arm I attached to upright member 62.

An amplifier I III has its input circuit controlled by cooperating contacts 2i and 23, the former being mounted on lever III and the other disposed in a stationary support.

The amplifier is controlled by the contacts, and controls intermittently, according to the operation of the contacts, a servomotor 24 having a shaft 25 provided with a gear III which drives an input gear III of a differential 25. A second input gear II! of the differential is driven by constant speed motor 21 which has a shaft I II on which is a gear H6 in mesh with gear III. Preferably, the effective rate of intermittently operable motor 24 is double that of constant speed motor 21. The mechanism actuated by the output of the differential will be described further and servesasacam beingusedtoadiust The shaft H of the constant speed motor drives a shaft 51 through'gears III which actuates an eccentric mechanism 56 for vibrating a dither spring 55 attached to the eccentric mechanism and lever III.

Cam 9. is supported by a shaft III which is free to translate and rotate in bearings III and I22.

A circular rack I23 disposed on the upper end of cam shaft IIII is in mesh with a pinion I fixed to the output shaft I25 of the differential 26 which serves to displace cam 90 in translation. In the present embodiment of the invention, as output displacement of shaft It! is a measure of true altitude, and the shaft is shown as driving a flexible shaft I for a computer by means of gears I21 and Ill. The differential output shaft I25 may be also used control a local indicating device to show true altihide. For this purpose a pointer II! attached to gear I21 is shown as cooperating with a scale Ill to indicate a measure of true altitude thereon. A

Cam i. has a gear ISI' secured thereto in mesh shaft II! coupled by gears I to a shaft II! on which is fixed a knob I". A scale I", shown in section, fixed to shaft III cooperates with alubber line Ill on a movable coaxially disposed ring I42 frictionally coupled to. and supported by a fixed plate I which carries an outer scale I to which lubber line III maybe positioned. Knob I36 is used for the cam in rotation. The cam my be who positioned in rotationfrom the output scribed to correct the position of the cam and also the position of scale I40 for the data represented by the displacement of the differential output shaft I". when the cam is turned by knob Ill, however, clutch Iii slips, so that bedepending from ycnd displacing the cam in rotation, adjustment of knob II! has no effect on the apparatus.

In a true altitude computing device cam is preferably laid out for translation in altitude, H, and rotation in mean absolute temperature, Tm. This temperature may be set into the device manually, and varied automatically, by the drive including clutch IBI, at about 1 Kelvin for each thousand feet change in altitude. The mean absolute temperature is taken as the arithmetical average of the static air temperature at the ground level, Tt, and the static air temperature at the airplane, Tp. This relation is shown in the following equation where and T =absolute air temperature at the airplane.

The air temperature at the airplane increases approximately 198 Kelvin per thousand feet, with decreases in altitude where temperature inversion does not exist. Consequently, the mean absolute temperature, Tm, will decrease at the approximate rate of .99 Kelvin per thousand feet of change.

In the present embodiment of the invention, the mean absolute temperature, Tm, is introduced into the system by knob I36 which positions cam 90 in rotation. The stationary outer scale I associated with knob I36 is calibrated according to Tt. Ring Ill which is frictionally supported by plate ill, is adjusted to position the lubber line I thereon opposite correct Tr value on stationary scale I. Dial I40 which is fixed with respect to knob I is calibrated for T and knob I36 is moved to position dial Illl with reference to lubber line I thereby displacing shalt IS! in the sum of T+T,. By introduclng a suitable ratio (1:2) in the gear train by which can 9| is rotated, the average of Tt and T, is obtained.

As stated above, Equation 5 shows that the arm I: of lever III is a measure of the ratio and com I may be laid out as to position fulcrum shaft ll accordingly. From Equations 1 and 5 Teno Equation 12 shows that the lift or travel I) of the cam follower rod II and fulcrum shaft 80 is a function of H and Tm. L is a constant, and the distance between the points of application of Pa and PT. The surface of cam 90 is laid out preferably according to Equation 12.

The flat springs I and ii supporting lever it have suilicient flexibility to permit limited rotation of the lever about fulcrum shaft 80, which movement is restricted by stops Ill and II to a small angle and therefore the angular displacement of the lever about its fulcrum is always small. The fulcrum shaft II is free to turn within the ball bearing rollers II and 82 when the fulcrum is displaced, and therefore, the shaft may freely roll on the under surface of lever it while the rollers II and 2 roll in the opposite direction on tracks 16 and I1, which provides a substantially frictionless arrangement for displacing the fulcrum. Because of the mounting of the lever with flat springs and the elimination of sliding friction by the use of rolling action to translate the fulcrum, static friction energy are kept at a minimum. Also, since the lever is operated as a null device and is never allowed to get far out of balance, the movement of the springs attached thereto is kept small and hence energy loss due to hysteresis of the spring support is minimized. The dithering arrangement is provided to eliminate further effects of any static friction that may be present, and when the frequency of the dither mechanism is set at approximately twice the natural oscillatory frequency of the unit, the amplitude of oscillation of the servo response can be reduced to a negllcible value.

In Fig. l constant speed motor 21 constantly drives into differential 26 in such direction that cam 90 is moved to displace carriage 81 and ful crum shaft ll toward the left of the drawing to displace lever It in a clockwise direction from a condition of unbalance, through a balanced condition and then into an unbalanced condition in the opposite direction. In the latter unbalanced condition contacts II and 2! engage thus operating amplifier H which causes the unidirectional intermittently operable motor 2! to drive into differential 15. Motor 2| drives the differential at double the rate of motor Il thereby reversing the direction of output shaft I of the differential which causes cam 90 to move in translation in the opposite direction thereby displacing the fulcrum shaft 80 towards the right of the drawing returning the lever to equilibrium and separating contacts 2! and II thereby stopping motor fl. As motor 21 is constantly operating. the cycle is repeated and the lever is maintained in a state of dynamic equilibrium about its fulcrum. With the lever in balanced position, which is the case when the servo unit is functioning properly, the translational force for the fulcrum shaft an would be theoretically zero. This is assumed by neglecting second order frictional forces and the force of spring 9! which holds cam follower 88 against the surface of cm ll.

when the instrument has been once adjusted, thepositionoffulcrumshaft Ilrequlredtobalancelever llwillvaryinaccordancewiththe output displacement of bellows l8 and since this position depends on the displacement of output shaft iii of thediiferential, this shaft. in the case of a true altitude meter. will provide a measure of hue altitude.

In a true altimeter where the cam BI is positinned-in rotation according to mean absolute temperature, Tm, which as explained above varies with altitude, the cam 9| is constantly displaced in rotation to correct Tm for changing altitude by gear I52 which is driven through friction clutch iii by the differential output shaft III.

Since knob I" is connected by a gear and shaft arrangement with the gear ill on cam DI, the position of knob Ill is also corrected as true altitude changes.

The novel force-ratio measuring instrument herein described will be seen to comprise a substantially fixed lever having one degree of freedom, namely rotation about its fulcrum. The amount of this rotation is variable according to a condition which determines the characteristics of the forces to be measured, which forces are applied at the ends of the lever. These forces may be applied at the ends of the lever by means of calibrated springs, either manually or automaticaily, and one or both may be substituted by mechanisms responsive to an ambient condition being measured. Thus, in the case of an altimeter, one end of the lever arm may be made responsive to static pressure at the airplane (Ps while the other end is made responsive to target pressure (Fr), applied manually through a callbrated spring. The variable fulcrum is responsive to unbalance of force-moments of the system. The relatively fixed lever is supported at, the fulcrum of pivot, by its special mounting, in such a manner that it rotates vertically thereon, without sliding frictional engagement therewith. The lever is further freed from any residual static (or Coulomb) friction, resulting from its special mounting, by dithering at a frequency approximately twice that of the natural frequency of the system. This dithering, coupled with the making and breaking of contacts, controls and intermittently operated unidirectional servomotor, through an amplifier, to permit the maintenance of the otherwise fixedly secured lever system in a state of dynamic balance about its pivot. The

differential output is utilized to deliver an out-- put corresponding to a function of the forceratio measurements in the system, and with torque, as well as without introducing extraneous or bulky equipment into the device. The instant device may be mounted permanently in a sealed casing, and the functional elements therein so constituted and arranged as to be susceptible of calibration and to permit the assembly to be utilized in a variety of systems.

The simplicity of the construction, and the normal regidity and fixity of the elements, which are coordinated and consolidated into an extraordinary, shock-proof, yet flexible unit, instantaneously responsive to variable control conditions, is made possible by the special uniplanar suspensory mounting of the control lever or balance arm 'of the system with a dynamic pivot or fulcrum. variable according to a predominating force, all coupled with the dithering at a suitable frequency.

The unitary mounting of such lever controlled, force-ratio measuring devices, in a single instrull ment, in substantially shock-proof assemblies, makesthedevicesespeciallysuitedforusein aircraft. and for Marine and Naval uses generally,andalsoforalluses,suchaslnvariousforms of artillery, gunnery, and otherlike installations, where extraordinary sturdiness and ability to function both positively and accurately, under the most adverse conditions, is an absolute prerequisite.

While the novel instrument herein has been described as comprising, in part, a casing having one inlet for the admission of an ambient control factor, namely static air pressure, it will be understood that any number of variable conditions may be introduced into the casing, and means provided in the casing for applying forces corresponding to the several conditions. or their resultants, in any combination, to the control lever in the manner and form specified hereinabove.

' Since many changes could be made in the above construction and many apparently widely diiferent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a force-ratio measuring instrument, a lever. a floating mounting arrangement therefor comprising a pair of flat springs secured respectively to opposite ends of the lever, the springs being disposed substantially in the plane of the lever at right angles to each other, a movable fulcrum for the lever. a pair of force applying means including a bellows, the force ratio of which is to be measured attached to the lever in opposition, spring means having a predetermined tension attached to the lever for counterbalancing the force applying means, means conauvma ingmeamforthelevertaidingtobhsthesame stantly tending to displace the fulcrum inone direction to unbalance the lever, an amplifier controlled bythe lever when thus unbalanced, a servomotor operated by the amplifier when thus controlled, 'a mechanism driven by the servomotor for displacing the fulcrum in the opposite direction whereby the fulcrum is caused to oscillate about a position wherein the lever is balinthedireetionoftheprediminatingforce,later y m a om membersatthsemoftbeleverandrespectlvely ilxedtothebracket,saidsuspensionmembersbeinsrespeetivciymoimtedinandatrlshtansles tothelongitudinalaxisofthelevenmeansfor reciprocatingthefulcrumonthebracketalong the longitudinal axis of the lever to vary the force-moments ofthe'levenmdrnthermeans coupledwithoneofthefomeapplyingmeansfor vibrating said lever.

4. In a force-ratio measuring instrument, in combination,acasing,aleverinthecaslng,a fulcrumforthelevenabracketsupportingthe fulcrum, a plurality of force applying means for the lever tending to bias the same in the direction of the predominating force, laterally-rigid, verticaily-flexible, coplanar mmenslon springs at the endsoftheleverandrespectivelyflxedtotbe bracketsaidsuspensionwringsbeingrespectively mounted in and at r t angle to the longitudinalaxisofthelevenmeansforreciprocating the fulcrum along the longitudinal axis of the lever to balance the force-moments thereof, and dither means coupled with oneof theforce applyingmeans forvibraiingsaklleverarmatatleast double its natural frequency of vibration.

5. In a force-ratio measuring instrument, in combination, a casing forming a plenum chamber, a lever, a bracket supporting the lever in the casing, laterally-rigid. vertically-flexible, coplanar suspension members at the ends of the lever fixed with respect to thecasing, at least one of said simpension members being mounted atrightanglestothelongimdinalaxisofthe levenafulcrumfortheleversimportedbyflie bracket, force-applying means and counter balancing means therefor attached to thelever forming with the suspens'lm members and the casing a normally shock-woof supporting system fortheleverwheninastateofrmsaidforce applyingmeansbeingresponsivetocontrolconditions to vary the force-moments of the lever about thefulerumandcauseunbalanceofthe lever and displacement thereof about the fulcrum in the direction of a predominating force-moment, and dither means coupled wifli the counter-balancing meam operahletovibratesaid lever at a frequency at least double its natural frequency, whereby the restaining effect of the supporting system is neutralized within predetermined limits without effecting the shock-proof beingdisposedsubstantiallyintheplaneofthelever and at right angles to each other, a movable fulcrum for the lever, a pair of force applying means for-the lever comprising'an evacuated beilows and a spring attached to the lever in opposition on opposite sides of the fulcrum, a pair of springs having a predetermined fixed tension attached to the lever so as to counter balance the respective force applying means. means for dithering the lever coupled with one of said springs, means responsive to an unbalanced condition of the lever for displacing the fulcrum to balance the lever, and an indicating device controlled by the last mentioned means in accordance with the position of the fulcrum.

3. In a forceratio measuring instrument, in combination, a casing, a lever in the casing, a bracket, a movable fulcrum for the lever supmounting of the lever.

6; A true altitude meter comprising a lever, a movable fulcrum therefor, force applying means for the lever including a bellows responsive to changingairpi-essureattachedtotheievena spring connected to the lever for applyi a predetermined tension to the bellows, means for cacillating the fulcrum about a position wherein the leveris in balanced condition to obtain a measure of the ratio of the forces applied thereto whichcomprisesacamlaidoutinaccordancc.

with functions of altitude and temperature for displacing the fulcrum, motor means for actuating the cam, including a constantly operating motor tendingtoturnthecaminone' directionat a predetermined rate and an intermittently, operable motor controllable by the lever when displaced in a predetermined direction from a balanced condition effective to turn the cam in the opposite direction at a greater rate, and an altitude indicating device actuated by the motor ported by the bracket, a plurality of force apply- 15 means in iixed relation with the eam.

7. A true altitude meter comprising a lever, coplanar flat suspension springs for the lever at the ends thereof, a movable fulcrum for the lever, a plurality of force applying means for the lever including a bellows responsive to cha ing air pressure attached to the lever, a spring effective to apply a predetermined tension to the bellows when the lever is in balanced condition, means for oscillating the fulcrum about a position wherein the lever is in balanced condition to obtain a measure of the ratio of the forces applied to the lever which comprises a cam laid out in accordance with functions of altitude and temperature for displacing the fulcrum, motor means for actuating the cam, including an intermittently operable motor controllable by the lever when displaced in a predetermined direction from a balanced condition, and an altitude indicating device actuated by the motor means in fixed relation with the cam.

8. A true altitude meter comprising a lever, a movable fulcrum therefor, a plurality of force applying means for the lever including a bellows responsive to changing air pressure attached to the lever, a spring connected to the lever for counterbalancing the initial bellows spring force applied thereto by the bellows, means for oscillating the fulcrum about a position wherein the lever is in balanced condition to obtain a measure of the ratio of the forces applied to the lever which comprises a cam laid out in accordance with functions of altitude and temperature for displacing the fulcrum, motor means for actuating the cam, the motor means including an intermittently operable motor, actuated by the lever when displaced in a predetermined direction from a balanced condition, an altitude indicating device actuated by the motor means together with the cam, and dither means connected with said spring for vibrating the lever.

9. A true altitude meter comprising a lever, coplanar, flat suspension members for the lever at the ends thereof, a movable fulcrum for the lever, force applying means for the lever includin a bellows responsive to changing air pressure attached to the lever, a spring connected to the lever for counterbalancing the initial bellows spring force applied thereto by the bellows,

means for oscillating the fulcrum about a position wherein the lever is in balanced condition to obtain a measure of the ratio of the forces applied to the lever which comprises a cam laid out in accordance with functions of altitude and temperature for displacing the fulcrum, motor means for actuating the cam, the motor means including an intermittently operable motor, means actuated by the lever when displaced in a predetermined direction from a balanced condition for controlling the intermittently operable motor, an altitude indicating device actuated by the motor means together with the cam, and dither means attached to the spring for vibrating the lever.

10. A true altitude meter comprising a lever, a movable fulcrum therefor, a plurality of force applying means for the lever including a bellows responsive to changing air pressure attached thereto, a spring for counterbalancing the initial bellows spring force applied by the bellows to the lever, means for oscillating the fulcrum about a position wherein thelever i in balanced condition to obtain a measure of the ratio of the forces applied to the lever which comprises a three dimension cam laid out in accordance with functions of altitude and temperature, means for displacing the cam in one dimension according to temperature, motor means for oscillating the came in another dimension including an intermittently operable motor, means responsive to the displacement of the lever in a predetermined direction from a balanced condition for actuating the motor, a follower for the cam operatively connected with the fulcrum and an indicating device actuated in fixed relation with the cam by the motor means.

11. A true altitude meter comprising a lever, coplanar, flat suspension members for the lever at the ends thereof, a movable fulcrum for the lever, a plurality of force applying means for the lever including a bellows responsive to changing air pressure attached thereto, means for counterbalancing the initial bellows spring force applied by the bellows to the lever, means for oscillating the fulcrum about a position wherein the lever is in balanced condition to obtain a measure of the ratio of the force applied to the lever which comprises a three dimension cam laid out in accordance with functions of altitude and temperature, means for displacing the cam in one dimension according to temperature, motor means for oscillating the cam in another dimension including an intermittently operable motor, means responsive to the displacement of the lever in a predetermined direction from a balanced condition for actuating the motor, a follower for the cam operatively connected with the fulcrum and an indicating device actuated in fixed relation with the cam by the motor means. a

12. A true altitude meter comprising a lever,

a movable fulcrum therefor, a plurality of force applying means for the lever including a bellows responsive to changing air pressure directly connected with the lever, a spring connected to the lever for counterbalancing the initial bellows spring force applied thereto by the bellows, means for oscillating the fulcrum about a position wherein the lever is in balanced condition to obtain a measure of the ratio of the force applied to the lever which comprises a three dimensional cam laid out in accordance with functions of altitude and temperance, means for displacing the cam in one dimension according to temperature, motor means for oscillating the cam in another dimension including an intermittently operable motor, means responsive to the displacement of the lever in a predetermined direction from a balanced condition for actuating the motor, a follower for the cam operatively connected with the fulcrum, an indicating device actuated in fixed relation with the cam by the motor means, and a device for ditherin the lever coupled therewith.

13. A true altitude meter comprising a lever. coplanar, flat suspension members for the lever at ,the ends thereof, a movable fulcrum for the lever, force applying means for the lever including a bellows responsive to changin air pressure directly connected with the lever, a spring connected to the lever for counterbalancing the initial bellows spring force applied thereto by the bellows, mean for oscillating the fulcrum about a position wherein the lever is in balanced condition to obtain a measure of the ratio of the forces applied to the lever which comprises a three dimensional cam laid out in accordance with functions of altitude and temperature, means for displacing the cam in one dimension accordin to temperature, motor means for oscillating the cam in another dimension including an intermittently operable motor, means responsive to the displacement of the lever in a predetermined direction from a balanced condition for actuating the motor, a follower for the cam operatively connected with the fulcrum, an indicating device actuated in fixed relation with the cam by the motor means, and a device for dithering the lever coupled therewith.

14. A force-ratio measuring device comprising a lever, a movable fulcrum therefor, a cam laid out according to functions of the forces being measured, a follower for the cam attached to the fulcrum for positioning the same, constantly operated means for displacing the cam and fulcrum to unbalance the lever about the fulcrum in one direction. intermittently operable servo means operatively coupled with the cam and actuated by the lever when thus unbalanced effective to displace the cam and the fulcrum in such direction as to restore the lever to balance and thereby disable the servomeans, and a plurality of force exerting means oppositely efiective on the lever, at least one of the last mentioned means being variable in accordance with changes in a force being measured.

15. A force-ratio measuring device comprising a lever, a movable fulcrum therefor, force exerting means at the ends of the lever including an evacuated bellows, coplanar, fiat suspension spring members for the lever at the ends thereof, a cam laid out according to functions of the forces being measured, a follower for the cam coupled with the fulcrum for positioning the same, constantly operated means for displacing the cam and fulcrum to unbalance the lever about the fulcrum, and means actuated by the lever when thus unbalanced effective to displace the cam and the fulcrum in such direction as to restore the lever to balanced condition.

16. A force-ratio measuring device comprising a lever, a movable fulcrum therefor, a plurality of means for exerting on the lever the forces whose ratios are to be measured including an evacuated bellows coupled with the lever tending to bias the same, laterally-rigid, vertically? flexible, coplanar, flat spring suspension members for the lever at the ends thereof located in the longitudinal axis thereof and at right angles thereto, a cam laid out according to functions of the forces being measured, a follower for the cam coupled with the fulcrum for positioning the same, constantly operated means for displacing the cam and fulcrum to unbalance the lever about the fulcrum in one direction, means actuated by the lever when thus unbalanced effective to displace the cam and the fulcrum in such direction as to restore the lever to balanced condition, the arrangement being such that the position of the fulcrum required to balance the lever is a measure of the ratio of the forces being measured. I

17. A force-ratio measuring device comprising a lever, a movable fulcrum therefor, a plurality of force exerting means oppositely connected to the lever including an evacuated bellows, laterally-rigid, vertically-flexible, coplanar, flat suspension spring members for the lever at the ends thereof disposed in the longitudinal axis of the lever and at right angles thereto, a cam laid out according to functionsof the forces being measured, a follower for the cam coupled with the fulcrum for positioning the same, a constant speed motor, a differential mechanism actuated thereby having an output shaft effective to displace the cam and fulcrum, said motor being effective normally to displace the cam and fulcrum to unbalance the lever about the fulcrum in one direction, an intermittently operable motor controlled by the lever when thus unbalanced, the last mentioned motor being coupled with the differential and effective to drive the output shaft in the opposite direction to restore the lever to a balanced condition, and forceratlo indicating means controlled by the output shaft.

18. A true altitude meter comprising a lever, a movable fulcrum therefor, laterally-rigid, vertically-flexible. coplanar suspension members at the ends of the lever in and at right angles to the longitudinal axis thereof, a bellows responsive to changing altitude connected to one end of the lever and a spring tensioned according to ground pressure connected to the lever to counterbalance the moment of the bellows, means for imparting an oscillatory movement to the fulcrum about a position wherein the lever is in a balanced condition thereon comprising a three dimension cam laid out in accordance with functions of altitude and temperature, a follower for the cam operatively connected to the fulcrum, means for displacing the cam in a first dimension according to temperature, a differential mechanism coupled with the cam, means for oscillating the cam in a second dimension through the differential mechanism comprising a pair of motors coupled with the differential mechanism respectively and alternately effective to actuate the cam in opposite directions, means for actuating one of the motors controlled by the lever on displacement thereof from a balanced condition. and an altitude indicating device jointly controlled by the motors.

19. A true altitude meter comprising a lever, a movable fulcrum therefor, laterally-rigid, vertically-flexible coplanar suspension members at the ends of the lever in, and at right angles to the longitudinal axis thereof, force applying means for the lever including a bellows responsive to changing altitude connected to the lever, and a spring connected to the lever tensioned according to ground pressure for counterbalancing the moment of the bellows, means for imparting an oscillatory movement to the fulcrum about a position wherein the lever is in balanced condition thereon comprising a three dimension cam laid out in accordance with functions of altitude and temperature, a. follower for the cam opera-' tively connected to the fulcrum, means for displacing the cam in one dimension according tov temperature, means for displacing the cam in a second dimension comprising a pair of motors eifectlve alternately to displace the cam in a second dimension in opposite directions. means for actuating one of the motors controlled by the lever on displacement thereof in a predetermined direction from a balanced condition, means coupled with the force applying means for dithering the lever, and an' altitude indicating device jointly operated by the motors.

20. A force-ratio measuring device comprising a lever, a movable fulcrum therefor, a three dimension cam laid out according to functions of the forcm being measured, a follower for the cam operatively connected with the fulcrum, manually operable means for displacing the cam in one dimension, oscillating means for displacing the cam in another dimension effective first to displace'the cam and fulcrum in one direction thereby unbalancing the lever, and intermittently operable servo means controlled by the lever when thus unbalanced for displacing the cam and fulcrum in the opposite direction to restore the lever to balanced condition, means comprising a friction drive coupling the oscillating means with the manually operable means to correct the position of the cam in said one dimension in accordance with the actuation thereof by the oscillating means, and an indicating device actuated by the oscillating means.

21. A true altitude meter comprising a lever, a movable fulcrum therefor, force applying means for the lever including a bellows responsive to changing air pressure, a spring connected to the lever for counterbalancing the moment applied thereto by the bellows, means for oscillating the fulcrum about a position wherein the lever is in balanced condition which comprises a three dimension cam laid out in accordance with functions of altitude and temperature, manually operable means for displacing the cam in one dimension according to temperature, motor means for oscillating the cam in another dimension including an intermittently operable motor, means responsive to the displacement of the lever in a predetermined direction from a balanced condition for actuating the motor, a follower for the cam operatively connected with the fulcrum, means for correcting the position of the manually operable means for changing altitude actuated by the motor means, and an altitude indicating device actuated by the motor means,

22. A true altitude meter comprising a lever, a movable fulcrum therefor, force applying means for the lever including a bellows responsive to changing air pressure, a spring connected to the lever for counter-balancing the moment applied thereto by the bellows, means for oscillating the fulcrum about a position wherein the lever is in balanced condition thereon, which comprises a three dimension cam laid out in accordance with functions of altitude and temperature, a follower for the cam operatively connected with the fulcrum, manually operable means for displacing the cam in one dimension according to temperature, motor means for oscillating the cam in another dimension including an intermittently operable motor for positioning the fulcrum to balance the lever, means controlled by the lever when in unbalanced condition for operating the motor, means for correcting the position of the manually operable means for changing altitude comprising a friction drive actuated by the motor means and an altitude indicating device actuated by the motor means.

ROBERT F. GARBARINI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,013,252 Pigott Sept. 3, 1935 2,220,164 List Nov. 5, 1940 2,398,470 Shivers Apr. 16, 1946 FOREIGN PATENTS Number Country Date 248,384 Great Britain May 25, 1927 407,903 Germany Jan. 5, 1925 

